Helicobacter pylori (hereinafter also referred to as H.pylori) is a Gram-negative rod (spirochete) that has several polar flagella. These organisms were named Helicobacter (bacteria that spiral) since they move by rotating these flagella. In addition, they are also characterized by being able to survive in the strongly acidic environment of the human stomach, and primarily infect the pylorus as is indicated by their name, pylori.
Human infection is thought to occur by oral infection. In the case of Japanese, infection through one-time well water is presumed to be the main infection route. Consequently, although infection is rare among young persons who grew up in an age of advanced water utility facilities, middle-aged to elderly persons older than age 50 have conversely been indicated as demonstrating as high infection rate of greater than 70%.
Warren and Marshall first detected and isolated H.pylori from gastritis patients in 1982. As a result of subsequent infection experiments independently conducted by Marshall in 1984, H.pylori was verified to be directly involved in the onset of acute gastritis. Subsequently, H.pylori has been strongly indicated to be involved in the onset of atrophic gastritis, gastric and duodenal ulcers, gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric cancer. At present, patients infected with H.pylori are recommended to undergo elimination treatment regardless of the presence or absence of symptoms from the standpoint of preventing these diseases.
Although chemotherapy using antibiotics such as Clarithromycin or Amoxicillin is comparatively effective for treatment, approximately 20% of patients were said to be resistant to treatment due to infection by resistant strains. There is concern that the proportion of resistant strains will increase rapidly in the future. Moreover, administration of these conventional antibiotics is frequently associated with the problems regarding safety during long-term administration and recurrence, thus creating the need for the development of a drug that is both effective and safe.